diff options
Diffstat (limited to 'tools/testing/selftests/sched_ext/cyclic_kick_wait.c')
| -rw-r--r-- | tools/testing/selftests/sched_ext/cyclic_kick_wait.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/tools/testing/selftests/sched_ext/cyclic_kick_wait.c b/tools/testing/selftests/sched_ext/cyclic_kick_wait.c new file mode 100644 index 000000000000..c2e5aa9de715 --- /dev/null +++ b/tools/testing/selftests/sched_ext/cyclic_kick_wait.c @@ -0,0 +1,194 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Test SCX_KICK_WAIT forward progress under cyclic wait pressure. + * + * SCX_KICK_WAIT busy-waits until the target CPU enters the scheduling path. + * If multiple CPUs form a wait cycle (A waits for B, B waits for C, C waits + * for A), all CPUs deadlock unless the implementation breaks the cycle. + * + * This test creates that scenario: three CPUs are arranged in a ring. The BPF + * scheduler's ops.enqueue() kicks the next CPU in the ring with SCX_KICK_WAIT + * on every enqueue. Userspace pins 4 worker threads per CPU that loop calling + * sched_yield(), generating a steady stream of enqueues and thus sustained + * A->B->C->A kick_wait cycle pressure. The test passes if the system remains + * responsive for 5 seconds without the scheduler being killed by the watchdog. + */ +#define _GNU_SOURCE + +#include <bpf/bpf.h> +#include <errno.h> +#include <pthread.h> +#include <sched.h> +#include <scx/common.h> +#include <stdint.h> +#include <string.h> +#include <time.h> +#include <unistd.h> + +#include "scx_test.h" +#include "cyclic_kick_wait.bpf.skel.h" + +#define WORKERS_PER_CPU 4 +#define NR_TEST_CPUS 3 +#define NR_WORKERS (NR_TEST_CPUS * WORKERS_PER_CPU) + +struct worker_ctx { + pthread_t tid; + int cpu; + volatile bool stop; + volatile __u64 iters; + bool started; +}; + +static void *worker_fn(void *arg) +{ + struct worker_ctx *worker = arg; + cpu_set_t mask; + + CPU_ZERO(&mask); + CPU_SET(worker->cpu, &mask); + + if (sched_setaffinity(0, sizeof(mask), &mask)) + return (void *)(uintptr_t)errno; + + while (!worker->stop) { + sched_yield(); + worker->iters++; + } + + return NULL; +} + +static int join_worker(struct worker_ctx *worker) +{ + void *ret; + struct timespec ts; + int err; + + if (!worker->started) + return 0; + + if (clock_gettime(CLOCK_REALTIME, &ts)) + return -errno; + + ts.tv_sec += 2; + err = pthread_timedjoin_np(worker->tid, &ret, &ts); + if (err == ETIMEDOUT) + pthread_detach(worker->tid); + if (err) + return -err; + + if ((uintptr_t)ret) + return -(int)(uintptr_t)ret; + + return 0; +} + +static enum scx_test_status setup(void **ctx) +{ + struct cyclic_kick_wait *skel; + + skel = cyclic_kick_wait__open(); + SCX_FAIL_IF(!skel, "Failed to open skel"); + SCX_ENUM_INIT(skel); + + *ctx = skel; + return SCX_TEST_PASS; +} + +static enum scx_test_status run(void *ctx) +{ + struct cyclic_kick_wait *skel = ctx; + struct worker_ctx workers[NR_WORKERS] = {}; + struct bpf_link *link = NULL; + enum scx_test_status status = SCX_TEST_PASS; + int test_cpus[NR_TEST_CPUS]; + int nr_cpus = 0; + cpu_set_t mask; + int ret, i; + + if (sched_getaffinity(0, sizeof(mask), &mask)) { + SCX_ERR("Failed to get affinity (%d)", errno); + return SCX_TEST_FAIL; + } + + for (i = 0; i < CPU_SETSIZE; i++) { + if (CPU_ISSET(i, &mask)) + test_cpus[nr_cpus++] = i; + if (nr_cpus == NR_TEST_CPUS) + break; + } + + if (nr_cpus < NR_TEST_CPUS) + return SCX_TEST_SKIP; + + skel->rodata->test_cpu_a = test_cpus[0]; + skel->rodata->test_cpu_b = test_cpus[1]; + skel->rodata->test_cpu_c = test_cpus[2]; + + if (cyclic_kick_wait__load(skel)) { + SCX_ERR("Failed to load skel"); + return SCX_TEST_FAIL; + } + + link = bpf_map__attach_struct_ops(skel->maps.cyclic_kick_wait_ops); + if (!link) { + SCX_ERR("Failed to attach scheduler"); + return SCX_TEST_FAIL; + } + + for (i = 0; i < NR_WORKERS; i++) + workers[i].cpu = test_cpus[i / WORKERS_PER_CPU]; + + for (i = 0; i < NR_WORKERS; i++) { + ret = pthread_create(&workers[i].tid, NULL, worker_fn, &workers[i]); + if (ret) { + SCX_ERR("Failed to create worker thread %d (%d)", i, ret); + status = SCX_TEST_FAIL; + goto out; + } + workers[i].started = true; + } + + sleep(5); + + if (skel->data->uei.kind != EXIT_KIND(SCX_EXIT_NONE)) { + SCX_ERR("Scheduler exited unexpectedly (kind=%llu code=%lld)", + (unsigned long long)skel->data->uei.kind, + (long long)skel->data->uei.exit_code); + status = SCX_TEST_FAIL; + } + +out: + for (i = 0; i < NR_WORKERS; i++) + workers[i].stop = true; + + for (i = 0; i < NR_WORKERS; i++) { + ret = join_worker(&workers[i]); + if (ret && status == SCX_TEST_PASS) { + SCX_ERR("Failed to join worker thread %d (%d)", i, ret); + status = SCX_TEST_FAIL; + } + } + + if (link) + bpf_link__destroy(link); + + return status; +} + +static void cleanup(void *ctx) +{ + struct cyclic_kick_wait *skel = ctx; + + cyclic_kick_wait__destroy(skel); +} + +struct scx_test cyclic_kick_wait = { + .name = "cyclic_kick_wait", + .description = "Verify SCX_KICK_WAIT forward progress under a 3-CPU wait cycle", + .setup = setup, + .run = run, + .cleanup = cleanup, +}; +REGISTER_SCX_TEST(&cyclic_kick_wait) |